When Does Grief Become Sin?

“Grief comes easily to me. The furnace of my many afflictions—stoked by painful bone disease, stage 4 cancer, advancing arthritis, perpetual 35-year-long head pain…. When you grieve as much as I have, you sometimes wonder what the Lord thinks of it. Is my grief permissible, or have I fallen into grieving doubt and self-pitying discontent?” - TGC